Pivotal squeegee mount with fluid bias

Abstract

A screen printing machine wherein a cylindrical stencil is rotatable about a horizontal axis and the liquid-supplying header in the stencil supports a carrier for a horizontal pintle pivotably mounting an elongated holder for a blade-like or rod-like squeegee. A gas-filled deformable cushion between the carrier and the holder biases the squeegee against the internal surface of the stencil opposite the locus where the external surface of the stencil contacts the material to be printed. Several helical springs which are attached to the holder and to the header bias the holder upwardly with a force which compensates for the combined weight of the squeegee and holder so that the force with which the squeegee bears against the internal surface of the stencil depends exclusively on the regulatable pressure of gaseous fluid in the cushion.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims: 
     
       1. In a screen printing machine, the combination of an elongated tubular liquid-permeable stencil having endless internal and external surfaces; means for moving said stencil in a predetermined direction relative to a moving web of material to be printed so that successive increments of said external surface contact successive increments of the web; stationary support means having portions located in the interior of said stencil for supporting a holder; a squeegee adjacent to and in contact with said internal surface along a line of contact; a holder for holding said squeegee and being pivotably supported on said portions of said support means so that said holder can turn about a pivot axis which extends transverse to the direction of movement of said stencil and is located ahead of said squeegee, as considered in said direction of movement; first biasing means for biasing said holder, said first biasing means being located above said holder upwardly of the line of contact between said squeegee and said internal surface, so as to urge said squeegee in vertical direction against said internal surface; and second biasing means engaging said holder and acting upon the same in opposition to said first-mentioned biasing means. 
     
     
       2. The combination of claim 1, wherein said support means comprises a plurality of brackets and a pintle mounted in said brackets. 
     
     
       3. The combination of claim 1, wherein said holder comprises a first portion pivotable about said axis, a second portion supporting said squeegee, and fastener means securing said second portion to said first portion. 
     
     
       4. The combination of claim 1, wherein said support means comprises a U-shaped portion and said first biasing means includes a gas-filled cushion received in said U-shaped portion. 
     
     
       5. The combination of claim 1, wherein said first biasing means comprises a deformable hollow cushion interposed between said support means and said holder and means for maintaining a supply of pressurized gaseous fluid in said cushion. 
     
     
       6. The combination of claim 5, wherein said squeegee comprises a doctor blade having an elongated edge portion engaging said internal surface, said axis being located in a horizontal plane which extends substantially midway between said edge portion and said cushion. 
     
     
       7. The combination of claim 1, wherein said second biasing means urges said holder in a direction to disengage said squeegee from said internal surface against the opposition of said first biasing means and with a force which compensates for the combined weight of said holder and said squeegee. 
     
     
       8. The combination of claim 7, wherein said pivot axis is substantially horizontal and said second biasing means comprises at least one spring connected to said holder at a point which is spaced from said axis. 
     
     
       9. The combination of claim 1, wherein said holder comprises a plurality of discrete portions and fastener means separably securing said portions to each other. 
     
     
       10. The combination of claim 9, wherein said portions of said holder have complementary parts which abut against each other and said parts have aligned external surfaces. 
     
     
       11. The combination of claim 1, wherein said support means includes a liquid supplying tube and a carrier secured to said tube, said holder being pivoted to said carrier. 
     
     
       12. The combination of claim 11, wherein said carrier has a concave surface and said first biasing means comprises a gas-filled cushion abutting against said concave surface. 
     
     
       13. The combination of claim 1, wherein said pivot axis is substantially horizontal and said squeegee is located at a level below said axis, said first biasing means comprising a gas-filled cushion abutting against said support means at a level above said axis and said holder having an upwardly projecting extension bearing against said cushion. 
     
     
       14. The combination of claim 13, wherein said support means has a concave recess for said cushion and said extension has a rounded external surface bearing against said cushion in said recess so as to impart to the cushion a substantially kidney-shaped profile. 
     
     
       15. The combination of claim 14, wherein said squeegee comprises a deformable blade having an edge portion engaging said internal surface, said extension and said blade having a common substantially vertical symmetry plane. 
     
     
       16. In a screen printing machine, the combination of an elongated tubular liquid-permeable stencil having endless internal and external surfaces; means for moving said stencil in a predetermined direction relative to a moving web of material to be printed so that successive increments of said external surface contact successive increments of the web; a holder; stationary support means having portions located in the interior of said stencil for supporting said holder; a squeegee mounted in said holder adjacent to and in contact with said internal surface along a line of contact; means for pivotably coupling said holder to said portions of said support means so that said holder can turn about a pivot axis which extends transverse to the direction of movement of said stencil and is located ahead of said squeegee, as considered in said direction of movement; first biasing means for biasing said holder, said first biasing means being located above said holder upwardly of the line of contact between said squeegee and said internal surface, so as to urge said squeegee in vertical direction against said internal surface; and releasable second biasing means engaging said holder and acting upon the same in opposition to said first-mentioned biasing means, said second biasing means being disengageable from said holder to permit pivoting of the same about said axis to a position in which said squeegee is freely accessible to an operator. 
     
     
       17. In a screen printing machine, the combination of an elongated tubular liquid-permeable stencil having endless internal and external surfaces; means for moving said stencil in a predetermined direction relative to a moving web of material to be printed so that successive increments of said external surface contact successive increments of the web; a holder; stationary support means having portions located in the interior of said stencil for supporting said holder turnable about a substantially horizontal axis; a squeegee mounted in said holder adjacent to and in contact with said internal surface along a line of contact; means for pivotably coupling said holder to said portions of said support means so that said holer can turn about a pivot axis which extends transverse to the direction of movement of said stencil and is located ahead of said squeegee, as considered in said direction of movement, said holder comprising a first portion which is pivotable about said axis, a second portion mounting said squeegee, and fastener means rigidly securing said second portion to said first portion; first biasing means for biasing said holder in a direction to move said squeegee away from said internal surface, comprising at least one eyelet provided on said second portion and a spring having a first portion affixed to said eyelet and a second portion affixed to said support means; and second biasing means located above said holder upwardly of the line of contact between said squeegee and said internal surface, for urging said squeegee in vertical direction against said internal surface. 
     
     
       18. The combination of claim 17, wherein said spring is a helical spring having a substantially vertical axis. 
     
     
       19. The combination of claim 18, wherein said eyelet is located at the level of said first-mentioned axis.